Broad band directive antenna



Sept. 1944. P. s. CARTE R 2,357,382

BROAD BAND DIRECTIVE ANTENNA Fil'ed Nov. 24, 1942 2 Sheets-Sheet 1 l2 3 4 5 s 7 a 9101i 12431415161718'I920 DISTANCE Axe/v CONN/C70,? W 2/ INVENTOR.

ATTORNEY Sept. 5, 1944. a J' 2,357,382

BROAD BAND DIRECTIVE ANTENNA Filed Nov. 24, 1942 2 Sheets-Sheet 2 k 3 5 o: k Q 4 2 3'4 5 6 7 a 9-l0 I! I2 I3 14 I5l6l7 13.1920 D/STA/VC' ALONG GJNDUCTOP //v A Tlcifi. I Pants/v1 50 35 530 k 25 m w 4 L 5 0 3.5 3.7 6.! 62 6.3 .14 6.5 METERS v2w v WAVE [ENGTH INVE NTOR PM; m 6? (42755.

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to have about twice as Patented Sept. 5, 1944 2,357,382 BROAD BAND DIRECTIVE ANTENNA Philip S. Carter, Rocky Point, N.

Radio Corporation of America, a

Delaware Y., assignor to corporation of Application November 24, 1942, Serial No. 466,721 16 Claims. (01. 250-33) The present invention relates to traveling wave antennas and, more particularly, to such antennas designed to cover a wide frequency band.

It has heretofore been customary, when desiring an antenna useable over a wide band'of frequencies, to utilize resistance terminated rhombic antennas. In usuing these antennas a high price'is paid in lost radiation efficiency, directivity. and in higher construction cost for the operating convenience of an aperiodic antenna. The usual resistance terminated rhombic type of antenna wastes about half of the transmitter output in the terminating resistance at the optimum operating frequency while at lower frequencies a much greater proportion of the power is lost. Since so much of the transmitted power is wasted in the resistance, the resistance terminated rhombic antenna must be designed much directivity to give a desired power gain in the desired direction as would be the case of other antennas having a higher radiation efllciency. Therefore, in using this type of antenna we must either be satisfied with a weaker signal or the" vertical and horizontal spread of angles covered by the beam must be reduced by increasing the antenna dimensions. Furthermore, the directivity of the rhombic antenna decreases more rapidly with the change in frequency than with that of a V antenna of equivalent dimensions.

An object, therefore, of the present invention is to provide an antenna system which is free of the foregoing objections.

Another object of the present invention is to provide a uni-directional traveling wave antenna of high efiiciency over a broad band of frequencies.

Still another object of the present invention is the provision of antenna, as aforesaid,.in which the losses caused by the terminating resistance are avoided.

A further object of the present invention is the provision of a traveling wave antenna whichv is operative without substantial frequency discrimination over a wide band of frequencies.

Still a further object of the present invention is the improvement of the directivity of traveling wave antennas.

A further object of the present invention is the provision of an unloaded V type traveling wave-antenna which is not adversely affected by a change in frequency.

The foregoing objects, and others which may appear from the following detailed description, are attained in accordance with the principles of adjacent ends by a transmission the present, invention by the provision of a traveling wave antenna, including one or more elongated conductors energized at one end and said conductors being characterized in that they are so arranged as to have uniform current distribution over the length thereof. This may be attained by forming the conductors in the form of cones energized at their apices or byterminating the conductors of the antenna in conductive conical surfaces of revolution. If the proportions of said conical elements are properly chosen reflection at the free ends of the conductors may, be avoided without using terminating resistances. Thus all of the energy applied to the wires is radiated and used to cause a sharply directive beam and none is wasted.

The novel features.which,.it is'believed, are characteristic of the present invention are pointed out with particularity in the appended claims. The invention will, however, be more completely understood by reference to the following detailed description which is accompanied by drawings in which Figure ment of the present invention, while Figure '2' illustrates a modification of a portion of the antenna of Figure 1 and Figure 3 illustrates a further modification of the invention, while Figure 4 is a curve illustrating the current distribution along the length of a conductor of a V antenna and Figure 5 is a curve illustrating the current distribution along a conductor of a V' antenna terminated by cones in accordance with one aspect of the present invention and Figure 6 is a curve showing the relationship between wavelength and percentage reflection on an antenna constructed according to the present in-] conductors II] and arranged at an angle to one another and energized at their more closely line TL connect ed to a suitable source of'high frequency energy. Each of the conductors in and II is composed of a pluralityvof wires arranged along the surface of an imaginary cone. The apices of the conical conductors are each connected to one of the conductors of transmission line TL while the base of the cone is formed by the wires being connected to spreader rings 22. Additional rings (not shown) may be spaced along the length of the conductor in order to maintain the conical relationship between the wires. Whileonly a conductors l0 and H, an actual physical em- 1 illustrates one embodifiguration and attached bodiment of the invention sixteen or more wires. The widely spaced ends of conductors i8, II are supported above ground by ropes 28 attached to supporting poles (not shown).

An embodiment of the form of the invention shown in Figure 1, using the dimensions shown in the figure, and operated at a frequency of 3.53 meters had a coeflicient of reflection of the order of 4.5 percent and less than 10 percent over a very wide range. This, it will be seen, is markedly better than the coeflicient of reflection of the order of 50 to 60 percent usually obtained with an unterminated V antenna utilizing single wires in each conductor.

In Figure 2 is shown a modification of one of th conductors of the antenna of Figure 1. Here, the conductor l has, as in the case of Figure 1, all of the wires terminating at a point where it is connected to one of the conductors of transmission line TL. For a portion of the length of the conductor the Wires are arranged in a conical configuration and maintained in this arrangement by spacing rings 32. Then, for the remainder of the length of the conductor the wires are arranged in a flattened fan-like conin vertical alignment through insulators 33 along supporting post 34. The conical portion of the conductor may be of the order of 48 feet or 14.6 meters or slightly less than half of the overall length of the order of 120 feet or 36.5 meters. No reflection whatever may be observed when the wavelength of the energy applied by the antenna by transmission line TL is varied over a range of from 6.1 meters to 6.5 meters. In this frequency range the length of the conductor l0 approximated 6 wavelengths. For higher frequencies where the length of conductor l0 approximates l0 wavelengths the reflection is observed to increase somewhat. It is believed that this may be due to the effect of the insulators, etc., at the junction of the cone and fan portions of the conductor.

The proportions of the conical conductors IO, N are so chosen as to give the same characteristic impedance as the wires of the transmission line TL feeding the antenna. The characteristic of an impedance V antenna with conical conmay actually employ ductors where on is the half angle of the V and the angle of revolution of the cone may be determined from the relation Z 120 log A further modification of the present invention is shown in Figure 3 wherein the conductors l0 and II are single wires terminated at the end remote from their point of connection to transmission line TL by conical structures 30 and 3|. The cones may be constructed of relatively thin sheet copper. The overall length of each of the conductors l0 and II may be of the order of 10 wavelengths with the conical end portions 30 and 3| having lengths of the order of .36 wavelength. Tests indicate that without the conical end portions the energy reflected back along the antenna wires near the middle thereof was of the order of 58 percent while addition of the cones 30 and 3| reduces the reflection to 27%; percent. Substituting cones constructed Of 16 wires each 12 feet or 3.65 meters in length and having a base diameter of the order 0118 inches or a little less than a half meter for the solid sheet metal cones causes a reduction of the .coeflicient of reflection along the antenna wires to a figure of the order asszss of 19.7 percent. An increase Of the wavelength to 3.73 meters is accompanied by a corresponding decrease in the reflection to 18.6 percent. Utilizing the same antenna at nearly double thewavelength making the length of the antenna-of the order of 5 wavelengths and the length of the conical terminating portions about a half wavelength increases the reflection on the antenna wires to 38 percent. Increasingthe diameter of the base circle of the cones from 18 inches to 28 inches or .85 meter reduces the reflection along the antenna to 11.7 percent at a wavelength of 3.65 meters and to 17.3 percent at 3.5 meters. Coefficients of reflection under 16 percent may be obtained for a very wide range of operating Wavelengths.

Curve 40 in Figure 4 illustrates the distribution of current along the length of a single conductor of an unterminated single wire V antenna such as that described above with reference to Figure 3 but with the terminating cones omitted. It will be noted that current loops of substantial amplitude are uniformly spaced along the entire length of the conductor, the maxima following line 4! and the minimum line 42. The ratio of the ordinates of lines 4| and 42 is of the order of 3.75, resulting in a coeificient of reflection of the order of 58 percent. Adding terminating cones such as shown in Figure 3 to the single wire V antenna results in a reduction in the difference of the ordinate values of lines 4| and 42 following the current maxima and minima of current curve 40 (Figure 5). There the ratio of maximum to minimum current values is only 1.29 resulting in a coeiiicient of reflection of only 12.7 percent. 7

The curves of Figure 6 illustrate the manner in which the percentage of'reflection varies with a variation of the wavelength applied to the antenna of Figure 3 utilizing wire cone terminations having the base circle diameters of 28 inches.

It will be noted that the maximum reflection in'the wavelength range from 3.5 to 3.77 meters, as indicated by curve 50, does not exceed 17 /2 percent with a minimum coefficient of reflection of the order of 12 percent at a wavelength of 3.66 meters. An increase in the Wavelength causes an increase of reflection up to a maximum of 46 percent at 6.2 meters and a minimum of 33 percent at 6.45 meters, as indicated by curve 5|. While I have illustrated particular embodiments of the present invention it should be clearly understood that the invention is not limited thereto since many modifications may be made in the-several elements employed and in their arrangement and it is, therefore, contemplated by the appended claims to cover any such modifications as fall within the spirit and scope of the invention. 1

I claim:

1. A traveling wave antenna, including a conductor having a length greater than at least several multiples of the operating wavelength, said conductor being coupled to wave transducer means at one end and tapering from a large transverse dimension at the free end toward said one end, said taper being so chosen that energy travels along said conductor solely from one .end to said free end.

2. A traveling wave antenna, including a conductor having a length greater than at least sevi eral multiples of the operating wavelength, said conductor being coupled to wave transducer means. at one end and tapering from a large rality of wires arranged along one end, said taper being so chosen that energy travels alongsaid conductor solely from one end toward said free end, the tapering portion of said conductor having a length of the order of .36

' to one wavelength.

3. A traveling wave antenna, including a conductor having a length greater than at least several multiples of the operating wavelength, said conductor being coupled to wave transducer means at one end and tapering from a large transverse dimension at the free end toward said one end, said taper'being so chosen that energy travels along said conductor solely from one end to said free end, said conductor including a plurality of wires arranged along the length of the surface of the cone.

4. A traveling wave antenna, including a conductor having a length greater than at least several multiples of the operating wavelength, said conductor being coupled to wave transducer means at one end and tapering from a large transverse dimension at the free end toward said one endysaid taper being so chosen that energy travels along said conductor solely from on end to said free end, said conductor including a plurality of wires arranged along the length of the surface of a cone having an apex angle of from 27 to 30 degrees.

5. A traveling wave antenna, including-a conductor having a length greater than at least several multiples of the operating wavelength, said conductor being coupled to wave transducer means at one end and tapering from a large transverse dimension at the free end toward said one end, said taper being so chosen that energy travels along said conductor solely from one end to said free end, said conductor including a plurality of wires arranged along the length of the surface of a cone for a portion of the length of said conductor and arranged in a flat fan formation at said free end.

6. A traveling wave antenna, including a conductor having a length greater than at least several multiples of the operating wavelength, said conductor being coupled to wave transducer means at one end and tapering from a large transverse dimension at the free end toward said one end, said taper being so chosen that energy travels along said conductor solely from one end to said free end, said conductor including a pluthe length of the surface of a cone for substantially half of the length of said conductor and arranged in a flat fan formation for the remainder of the length of said conductor.

7. A traveling wave antenna, including a pair of conductors arranged in a V formation, said conductors being coupled to wave transducer means at the apex of said V, each of said conductors tapering from a large transverse dimension at their free ends toward the apex of said V, said taper being so chosen that energy travels along said conductors solely from the apex of said V to said free ends.

8. A traveling wave antenna, including a pair of conductors arranged in a V formation, said conductors being coupled to wave transducer means at the apex of said V, each of said conductors tapering from a large transverse dimension at their free ends toward the apex of said V, the taper of said conductors being so related to the angle between said conductors that no reflection of energy takes place from said free ends of said conductors.

9. A traveling wave antenna, including a pair of conductors arranged in a V- formation, said conductors being coupled to wave transducer means at the apex of said V, each of said conductors tapering from a large transverse dimension at their free ends toward the apex of said V, the taper of said conductors being so related to the angle between said conductors that no reflection of energy takes place from said free ends of said conductors, each of said conductors including a plurality of wires arranged along the length of the surface of a cone. 7

10. A traveling wave antenna, including a pair or conductors arranged in a V formation, said conductors being coupled to wave transducer means at the apex of said V, each of said 0011- ductors tapering from a large transverse dimension at their free ends toward the apex of said V, the taper of said conductors being so related to the angle between said conductors that no reflection of energy takes place from said free ends of said conductors, each of said conductors including a plurality of wires arranged along the length of the surface of the cone for substantially half the length of each of said conductors adjacent the face of said V and said wires being arranged in a flat fan formation at said free ends. 11. Atraveling wave antenna, including a pair of conductors arranged in a V formation, said conductors being coupled to wave transducer means at the apex of said V, each of said conductors tapering from a large transverse dimension at their free ends toward the apex of said V, the taper of said conductors being so related to the angle between said conductors that no reflection of energy takes place from said free ends of said conductors, each of said conductors including a plurality of wires arranged along the length of the surface of the cone for substantially half the length of each of said conductors adjacent the face of said V and said wires being arranged in a fiat fan formation at said free ends, the plane in which the free ends of said conductors of said fan formation lie, being vertical.

12. A traveling wave antenna, including a. conductor having a length greater than at least several multiples of the operating wavelength, said conductor being coupled to a transmission line at one end and tapering from a large transverse dimension at the other end toward said one end, said taper being so chosen that energy travels along said conductor solely from one end to said other end.

13. A traveling wave antenna, including a conductor having a, length greater than at least several multiples of the operating wavelength, said conductor being coupled to a transmission line at one end and tapering from a large transverse dimension at the other end toward said one end, said taper being so chosen that energy said V to said other ends.

I 15. A traveling wave antenna, including a pair of conductors arranged in a V formation, said conductors being coupled to a transmission line at the apex of said V, each of said conductors tapering from a large transverse dimension at their other ends toward the apex of said V, the taper of said conductors being so related to the angle between said conductors that no reflection of energy takes place from said other ends of said conductors, each of said conductors including a plurality of wires arranged along the length of the surface of the cone for substantially half the'length of each of said conductors adjacent the face of said V and said wires being arranged in a flat fan formation at said other ends.

PI-HLIP S. CARTER. 

